The effect of bacteriocins produced by Lactococcus lactis subsp.
Lactis ATCC 11454 (T1); Lactobacillus acidophilus JCM 1229 (T2);
Lactococcus lactis subsp. lactis ATCC 11454 & Lactobacillus acidophilus
JCM 1229 (T3) and bacteriocin extracts from Lactococcus lactis subsp.
lactis isolate (T4); Lactobacillus acidophilus isolate (T5); Lactococcus
lactis subsp. lactis & Lactobacillus acidophilus isolates (T6) as a natural
preservative in yoghurt compared with control yoghurt (C1) and yoghurt
with nisin (C2) were evaluated. Use of nisin and bacteriocins produced or
extracted with a level of ~100 AU/ml. Yoghurt samples were assessed for
coagulation time, chemical analysis, rheological properties, microbiological
quality, bacteriocin activity, sensory evaluation and shelf-life during
storage for up to 28 days at ~ 5°C. Yoghurt treated with nisin or
bacteriocins produced or extracted by some LAB increased coagulation
time compared with control yoghurt. Existence of bacteriocins retarded
growth of lactic acid bacteria, thereby delaying acid production.
Progressive increases in acid production during storage were observed in
control yoghurt compared with bacteriocins-treated yoghurt. The
rheological properties, sensory evaluation and shelf-life of yoghurt were
improved, when nisin and bacteriocins were used. The quality and shelflife
of yoghurt containing extracted bacteriocins or nisin were still
acceptable after 28 days of storage (T4, C2, T6 and T5 respectively)
2
followed, after 21 days with yoghurt containing bacteriocin producing
bacteria (T1, T3 and T2 consequently) compared to 14 days for control
yoghurt. It was concluded that the addition of bacteriocins extracted or
nisin (~100 AU/ml) to milk could be produce yoghurt with good
organoleptic properties and prolonged the shelf-life. |
